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    <title>ShellCheck: SC2321 – Array indices are already arithmetic contexts. Prefer removing the `$((` and `))`.</title>
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    <h1>SC2321 – ShellCheck Wiki</h1>
    <a href="https://github.com/koalaman/shellcheck/wiki/SC2321">See this page on GitHub</a>
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    <h2
id="array-indices-are-already-arithmetic-contexts-prefer-removing-the--and-">Array
indices are already arithmetic contexts. Prefer removing the
<code>$((</code> and <code>))</code>.</h2>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC2321.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="va">values</span><span class="op">[</span><span class="va">$((i</span><span class="op">+</span><span class="dv">1</span><span class="va">))</span><span class="op">]=</span>1</span></code></pre></div>
<h3 id="correct-code">Correct code:</h3>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC2321.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="va">values</span><span class="op">[</span>i+1<span class="op">]=</span>1</span></code></pre></div>
<h3 id="rationale">Rationale:</h3>
<p>In indexed arrays (but not associative ones), the array index is
already an arithmetic context. There is no point or value in wrapping it
in an additional, explicit <code>$((..))</code>.</p>
<h3 id="exceptions">Exceptions:</h3>
<p>If ShellCheck has failed to realize that your array is associative,
or if you for stylistic reasons prefer the redundancy, you can ignore
this message.</p>
<h3 id="related-resources">Related resources:</h3>
<ul>
<li>Help by adding links to BashFAQ, StackOverflow, man pages, POSIX,
etc!</li>
</ul>
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